The current invention is directed to a safe ended type end for a container. More specifically, the current invention is directed to an end for a container having improved opening characteristics.
Many products, such as food stuffs, including potato chips, as well as other articles, such as tennis balls, are packaged in containers having an easy open end 2, such as that shown in FIGS. 1-3. Conventionally, such ends are formed from metal plate, such as aluminum, having a thickness t of about 0.0095 inch (0.24 mm). Such ends have a circular score line formed between the central panel 8 and the rim 10. The rim 10 has a curl 17 formed thereon for attachment to the side wall of the container. A tab 4, attached by a rivet 5 to the central panel 8, is employed to effect opening. By pulling up on the end 7 of the tab 4, the nose 6 of the tab presses against the rim and causes the score line 12 to shear, thereby separating the central panel 8, which is discarded, from the rim 10. The minimum pulling force exerted on end of the tab 4 that is required to cause the initial shearing of the score line 12 is referred to as the xe2x80x9cpop value.xe2x80x9d After initial shearing, continued manipulation of the tab allows the user to completely sever the central panel from the rim portion by shearing the score line along its entire circumference. The force necessary to continue the shearing of the score line after the initial severing is referred to as the tear force. The lower the pop value and the tear force, the easier it is for the user to open the container.
The opening operation described above can result in a sharp edge being formed on the rim 8, which can result in a cutting hazard to the user. This rim edge can be made safe by folding under a portion of the rim 10 adjacent the score line 12 inwardly and then outwardly so as to form an upper fold 16 and a lower fold 14, with the bend 18 of the lower fold projecting radially inward beyond the score line 12 so as to protect the user from the sharp edge formed on the rim when it is severed along the score line, as shown in FIGS. 1-3.
The opening process also results in a sharp edge on the central panel. This central panel edge can be made safe by folding under a portion of the cental panel adjacent the score line 112 outwardly and then inwardly so as to form an upper fold 121 and a lower fold 117, with the bend of the lower fold projecting radially outward beyond the score line 112 so as to protect the user from the sharp edge formed on the central panel when it is severed along the score line, as shown in FIG. 4. In this type of can end, folds 115 and 123 are also formed in the rim portion 110, as discussed above. However, in this case, the rim folds are located above the score line, rather than below it. A can end having a folds in both the rim and the central panel is more fully disclosed in U.S. Pat. No. 3,986,632 (Morrison et al.), hereby incorporated by reference in its entirety.
Conventionally, the folds are tightly formed. For example, an easy open end made by the assignee of the current invention is made from metal plate having a thickness t of about 0.0095 inch (0.24 mm). As shown in FIG. 3, the vertical gap G1, by which the upper surface of the bend 18 of the lower fold 14 is displaced below the lower surface of the rim 10, has a width W1 in the vicinity of the score line 12 that is typically less than the thickness t of the plate and may often be less than one-half the thickness t of the plate and is sometimes even zero, so that the upper surface of the bend 18 contacts the lower surface of the rim portion 20. The width W2 of the vertical gap G2, by which the lower surface of the bend 19 in the upper fold 16 is displaced above the upper surface of the lower portion of the rim 10, is typically approximately equal to one or two times the thickness t of the plate. The overall height H of the folds 14 and 16 is typically no more than about six times the thickness t of the plate.
Unfortunately, the tightness of the folds can undesirably increase the difficulty of initially shearing the score line 12xe2x80x94that is, increase the pop value. As shown in FIG. 3 the width W1 of the gap G1 is minimal. Consequently, in order for the nose 6 of the tab 4 to create sufficient downward deflection in the upper portion 20 of the rim 10 to shear the score line 12, it must apply sufficient force F to also downwardly deflect the underlying bend 18 in the lower fold 14. This situation, which is sometimes referred to as xe2x80x9clockoutxe2x80x9d, increases the pop value.
The tightness of the folds can also increase the tear force, especially in ends that have folds on both the central panel and the rim panel. In such ends, further manipulation of the tab 5 and tearing of the score around its circumference after the initial pop causes the central panel 8 to bend along line Axe2x80x94A shown in FIG. 1. As shown in FIG. 4, this deformation causes the periphery of the central panel to locally bow at locations B, which are typically at approximately the 10:30 o""clock and 1:30 o""clock locations. This bowing causes the severed edge 109 of the central panel 108 to contact the bend in the rim fold 115 above it so that additional force must be applied to the tab 104 in order to effect continued shearing of the score line 112, thereby increasing the required tearing force.
Although easy open ends can be made, and have been made, with uniformly large gaps around the entire circumference of the fold, such as that disclosed in U.S. Pat. No. 5,105,977 (Taniuchi), such an arrangement can compromise the safety afforded by the fold if the upper portion 20 of the rim 10 does not spring completely down against the underlying fold after the central panel 8 has been removed.
Consequently, it would be desirable to create a easy open container end that is safe and yet is also easy to open.
It is an object of the current invention to provide an easy open safety container end with improved opening characteristics. This and other objects is accomplished in an easy open safety container end comprising (i) a central portion, (ii) a rim portion surrounding the central portion, the rim and central portions having a thickness and separated by a score line, (iii) means for applying a force to a portion of the end proximate the score line, and (iv) first and second circumferentially extending folds formed in the end adjacent the score line. The first fold is displaced from a portion of the end proximate the score line by a circumferentially extending gap, with a first circumferentially extending portion of the gap being less than the thickness and a second circumferentially extending portion of the gap being greater than the thickness. In a preferred embodiment of the invention, the second portion of the gap is greater than twice the thickness and encompasses an angle between about 2xc2x0 and 45xc2x0. The first portion of the gap is less than one half the thickness.
The current invention also encompasses an apparatus for forming an easy open container end, comprising upper and lower forming tools having opposing forming surfaces for forming a circumferentially extending fold in the container end, a first recess formed in at least one of the opposing forming surfaces, at least one of the forming tools movable toward the other of the forming tools whereby the recessed portion of the forming surface forms a first circumferentially extending portion of the fold and the remaining portion of the forming surface forms a second circumferentially extending portion of the fold, the first portion of the fold being looser than the second portion of the fold.